Cathode-ray tube



Aug 29, 1950 M. E. AMDURSKY 2,520,9@

CATHODE RAY TUBE Filed oct. ze, 194e AGENT Patented Aug. 29, 1950 UNITED STATES PATENT OFFICE |CATHDE-RAY Mark E. Amdursky, New York, -N. Ya assigner to Philips Laboratories, Inc., Irvington on Hudson, N fY.

3 Claims.

My invention relates tocathode `raytubesand more particularly to cathode ray tubes used Lin television.

In cathode `ray tubes used yfor television'reception, it is common -to employ an 4image screen which is fluorescent, and which luminesces'in response to a beam of cathode rays-impinging on the screen. -In tubes used for -televisiontransmission, itis common vto employ a light responsiveiniage screen `upon whiclris focused the picture to be televised, and a Abeam of cathode rays impinging on the screen is `employed -to-l develop an electrical signal corresponding to the-screen response. The invention will be more particularly described in connection with cathode ray television receptiontubes,-althoughit will be apparentto those skilled in the art/that it is equally applicabieto transmission tubes.

In a cathode ray television reception tubeyit has been suggested to -use a vspherical lmirror which gathersthe light fromthe luminescent image screen and reflects it through anaspherical correction plate lwhich refracts the light rays to correct the spherical aberration introducedby the mirror, so that when the televised image is cast on a viewing screen it there appears'with substantially no distortion. It has been 'further suggested to construct thetube with the mirror and correction plate as integral parts thereof. However, the construction of such internal optics tubes has been attended heretofore with lmany diflculties, and particularly with the diiculty of obtaining accurate initial optical alignment of the screen, the mirror, and the correction plate.

Therefore, it is one Vobjeetfof my invention to improve the-construction of cathode ray tubes employed in television.

It is a further object of the invention to provide a cathode ray 'television tube which is initially aligned with great optical accuracyfland which maintains this alignment.

VAnother/object of the invention -is to lprovide a superior and improvedmethod for the-assembly and construction of -a'cathode ray tube used in television.

Other objects, advantages,l and 'novel features of the invention will become apparent'asthe specification progresses.

In accordance'withlmy'invention the foregoing objects are achieved by constructing a tube wherein the image screen, the mirror, and the correction plate are an integral optically aligned unit. I have found that when a supporting framework is employed to position accurately the screen, the mirror, and the correction plate Vin .optically tested alignment, and the tube thereafter assembled Vwithout Vdisturbing this align- `ment,anopticallysuperior image is formedby the televisionsystem of -which the tube is apart. :In orderfthat the inventionmay be more clearly understood and readily carried into eifectfit will now be'fdescribedwith reference to the accompanying-drawing `in which the sole ligure is a longitudinal cross-section of a television projection Ytube vconstructed and assembled inl a preferred form of the invention. y

Referring now to thedrawing, a television projection tube lll-has acylindrical bulbous end porltion Il and athroat portion l2. 'An-electron gun i3 -is included in the throat portion so that the cathode rays, or electrons,impinge upon screen I4 on member Yllclfto form thereon theimage to be projected. The'gun is illustrated more or less schematically, as the various elements thereof are well knownl to the-art. Leads are'brought out at -the base of the tube to pins I5. The light from screen I4 strikes spherical mirror I6 and is reiiected thence throughV aspherical correction plate I8. "Central aperture 20 in Vmirror 16 provides free passage for the cathode rays,.'there through so that they may be swept lacross the screen to-cause luminescence and produce"V the image in known fashion. Struts 22,of which I prefer to use four, are attached at one end lto correction plate YI8 near ythe periphery thereof, and at the'other end` to mirror i6 -nearthe periphery thereof. y

-Brackets 2li are attached totwo of the struts. Spider elements 26 extend from two of the brackets toward the optical axis and t slideably into tie rod 28. The spiderelements are provided at their ends with broadened-portions@ and slots29a therein -to permit entry of screws 3G and allow the spider elements 26A tomove-normally to theplane of thegure. Screws 30 engage inthreads provided therefore in brackets 24J-Because of the-slottedtting of tie `rod=28-to spider elements 26, ythe-rod may-move normally'to fthe axisof the 'tube tothe right'or left asview'eddn the ligure, andset screws-32 threaded finto the tierod allowy such an adjustmentfwhenmade, to be rigidly fixed. A thumb screw 34 -is snugly fitted through 'Y tiey rod 28 centrally and is Afthreadtxl into member '14a -supportingscreen lll. Acornpressionalfspring 36 exerts Irressure between 'tie rod 28 and screen member Ma, thereby permitting the screen to be axially adjusted YVaccurately depending on 'how yfar screw34 'is threaded into the member. Attached to each fof` 4'struts 22 v*at `a calculated intermediate portion thereof are snubbers 5!! bearing against the cylindrical wall of end portion I I in order to better support and shock protect the elements of the tube. A certain amount of adjustability is also provided for positioning mirror I6 by screws 52 threaded into each strut with springs 54 holding the mirror firmly against the shoulders of the nuts.

In preparing the projection tube for assembly, I first prepare the face plate and have joined thereto the struts. It will be understood that calculations for the proper curvature of correction plate I8, mirror I6, and screen I4 and their relative positions have been made previously. The spider assembly including the screen I4 and the mirror I6 are then aflixed. The computations previously made will determine to a close approximation the length of the struts 22 and the position along them at which the spider members 24 are to be attached. The screen and mirror are then tentatively attached and the optical assembly is ready for final optical alignment. The optical alignment may be accomplished by taking the assembly into a dark room, casting a light, preferably a small intense parallel beam against screen I4 through aperture 20. A viewing screen 56 is placed along the optical axis of the system at the same distance from plate I8 at which the viewing screen is to be employed in the projection television system for which the tube is designed. Then I adjust the relative positions of correction plate I8, screen I4, and mirror I5 by means of the screws 26, 34, and 52 and moving tie rod 28 and members 26 until I have attained a sharp clear image u'pon the viewing screen of image screen I5. Other procedures for the final optical alignment will be apparent to those skilled in the optical art. Thereafter, screws 30 and 32 being tightened into position, and alignment optically re-checked, y.

I find it convenient to lightly spray the various screws with a quick drying adhesive substance which will substantially lock them in place against the possibility of inadvertent motion. The cylindrical walls of the bulbous portion I I of the tube and the throat portion I2 are separately prepared with the electron gun parts in yplace in the tube. Then I slip the optically aligned assembly comprising the correction plate, the screen, and the mirror all assembled on the supporting framework, into the tube with the snubbers in place. The periphery of the correction plate Where it abuts upon shoulders 6!) of the side Walls may now be gradually and uniformly heated until an air tight seal is made between the correction plate and the walls of the tube.

The tube may then be evacuated in conventional manner and is ready for use. It will be apparent that by my novel construction and method of assembly, the screen, the mirror, and the correction plate of the tube are maintained in accurate critical optical alignment for the life of the tube. The adjustment is much closer than that which has been provided by other methods and types of construction, and more accurate alignment is achieved than by mere mechanical methods While I have described my invention with a specific example and application, other variations will suggest themselves to those skilled in the art Without departing from the scope and spirit of the invention as defined in the appended claims.

What I claim is:

1. A cathode ray tube for television comprising an envelope having an open ended body portion,

and as an integral part of said tube a prefocussed optical projection system within said body portion, said system being initially focussed prior to assembly in the said body portion and remaining in precise optical alignment throughout the life of the tube and comprising an image screen, a mirror, a correction plate, and means independent of said body portion for securing said screen, said mirror and said correction plate in optical alignment relative to each other.

2. A cathode ray tube for television comprising an envelope portion having an open ended body portion, and as an integral part of said tube a prefocussed optical projection system Within the said body portion said system being initially focussed prior to assembly in the said body portion and remaining in precise optical alignment throughout the life of the tube and comprising a fluorescent image screen, a mirror, a correction plate, and means independent of the said body portion for securing said screen, said mirror and said correction plate in optical alignment relative to each other.

3. A cathode ray tube for television comprising an envelope having an open ended body portion and as an integral part thereof a prefocussed optical projection system within the said body portion said system being initially focussed prior to assembly in the said body portion and remaining in precise optical alignment throughout the life of the tube and comprising an image screen which fiuoresces when a beam of electrons strikes said screen and provides a luminescent image, a spherical mirror disposed within said body portion for projecting the luminescent image on said screen to the front of the tube, said mirror being provided with a centrally disposed aperture to permit passage of a beam of electrons which strikes the screen, an aspherical correcting element disposed in font of said mirror and behind said screen and constituting the front wall of the tube, a spider element for supporting said screen in precise optical relationship between said correcting element and said mirror, means for supporting the screen, mirror, and correcting element within the tube and independent of the said body portion, and means for prealigning said mirror, said screen and said correcting plate in precise optical relationship before insertion into the said body portion and thereafter maintaining the precise optical alignment.

MARK E. AMDURSKY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,060,825 Ressler` Nov. 17, 1935 2,139,678 Glass Dec. 13, 1938 2,295,779 Epstein Sept. 15, 1942 2,299,047 Winans Oct. 13, 1942 2,415,311 Szegho Feb. 4, 1947 2,440,735 Cawein May 4, 1948 2,440,736 Cawein iMay 4, 1948 2,467,462 Brown Apr. 19, 1949 FOREIGN PATENTS Number Country Date 452,148 Great Britain Aug. 17, 1936 557,771 Great Britain Dec. 3, 1943 487,241 Great Britain June 16, 1938 

